Ultra short wave system



July 16, 1946. Dow 2,404,279,

ULTRA SHORT WAVE SYSTEM Filed Aug. 7, 1941 BL OWER FLU/D COOL/N6 DUCTINVENTOR ORV/LLE E.- 00w BY ATTORNEY Patented July 16, 1946 ULTRA SHORTWAVE SYSTEM Orville E. Dow, Port J eiferson, N. Y., assignor to RadioCorporation of America, a corporation of Delaware Application August 7,1941, Serial N 0. 405,737

Claims.

This invention relates to ultra short wave apparatus for useparticularly with electron discharge device circuits.

One of the objects of the present invention is to provide a simplifiedand efficient electromechanical construction for a cavity resonator,

whose resonant frequency is readily adjustable,-

for use at ultra short waves.

Another object of the present invention is to provide improvements inthe method of and means for applying a magnetic field to the cavityresonator for focussing the electron beam passing through the interiorof the electron discharge device.

A further object is to provide an improved coupling circuit for usebetween the cavity resonator and a useful load, in which adjustments indamping and tuning or in tuning alone can be easily and accurately made.

A further object is to provide a cooling system for the resonator andassociated electron discharge device, wherein' the linkage between thehigh frequency apparatus and the blower duct is electrically shielded.

Numerous features of the present invention reside in the novelmechanical constructions employed (1) in the coupling circuit, wherebyboth the tuning and the damping can be changed independently; (2) in theapparatus employed for controlling the amount of the magnetomotive forcerequired for focussing the electron beam; (3) in the adjusting means forvarying the resonant frequency of the resonator by adjusting the lengthof its gap; and (4) in the flexible metallic bellows arrangement forsimplifying the assemblage of the resonator and the air duct carryingcooling fluid from the blower to the resonator.

Other objects and features will appear from a reading of the followingdescription which is accompanied by a drawing whose single figureillustrates, in section, a preferred form of ultra short Wave electrondischarge circuit embodying the principles of the invention. Since theinvention is primarily concerned with improvements in the mechanicalconstruction, the vacuum tube apparatus is merely shown in outline.

Referring to the drawing in more detail, there is shown an electrondischarge device I, comprising a vacuum tube structure consisting of anevacuated glass envelope 2' containing therein a cathode 3, the heater4, a modulating grid 5, ring-like accelerator electrodes 6, and acollector electrode 1, the latter containing therein a suitablesuppressor electrode, not shown. This type of electron discharge deviceis now well known in the art and is not being claimed per se, theshowing being given merely to illustrate how it fits into the resonatorstructure and associated apparatus constituting the invention. For amore detailed description of the electron discharge device with Zresonators and coupling circuits generally equivalent to those shown inthe drawing, reference is made to copending applications Serial Nos.296,045 and 346,106, respectively filed September 22, 1939, by Fred H.Kroger, and July 18, 1940, byOrville E. Dow. v V

Surrounding the exterior of the glass envelope 2 in symmetrical fashion,and located interrnediate the two accelerator electrodes 6, there isprovided the high Q, low-loss tank circuit 12 in' the form of a cavityresonator constituted by a copper cylinder l3 whose ends are closed bytruncated cones made of sheet copper Hl'and l5.

The dimension of the tank support, as measured from the center of theglass envelope 2 toward the arc of the sector shown in dotted lines atM, is approximately one-quarter of the length of the communication wavecorresponding to the resonant frequency. It should be noted that theshape of the resonator l2 departs somewhat from that shown in thecopending applications, supra, mainly in the lengthening of theresonator at the extreme edges and in the shortening of the resonator'atthe center due mainly to the provision of the cylindrical element I3.This'de-' parture in shape of the resonator from a true are sector doesnot deleteriously affect the operation of the resonator. resonantfrequency of the cavity resonator M to a limited degree, there isprovided an adjust-' able gap [6, one side of'which is formed by acopper plated iron sleeve l9, movable in a man ner describedhereinafter, and the other side of which is formed by an iron pole piecel! as a consequence of which there is obtained a variation of thecapacity between sides l9 and H of the gap. Sleeve I9 is made to move inan axial direction and makes sliding contactwith beryllium coppersprings l8, which are soldered to copper side [5 of the resonator.Sleeve I9 is preferably copper plated in order to provide low loss and agood electrical connection between elements l5 and I9.

For focussing the electron beam there are pro vided a. pair of magneticlenses'in series relation constituted by magnetic gaps l6 and 20 formed.respectively, by the spaced iron sleeves l1 and i9 and spaced ironsleeves l9 and 2|, all of which surround the glass envelope I and areserially arranged with respect to an iron magnetic path. This magneticpath includes an iron yoke which is placed adiacent to the sidesofonesector" one-quarter of an inch thick, they may, if desired,

be formed of separate elements, as shown. The ring-like permanent magnet30 is preferably made In order to vary the:

Although elements 28, 21 and 22 .are

3 of Alnico material and is held in fixed position by the iron polepieces I1 and 29. The magnetic flux will obviously flow through th pathmentioned above and across the magnetic gaps i8 and 20. The threadedring or sleeve 3| is made of brass and is integrally connected to thethreaded.

ring 23. Because. ring 3| is made of brass which has the same magneticpermeability as air, there is a magnetic gap 20 provided betweenelementsl9 and 2|. In order to adjust the effective magnetomotive force of thepermanent magnet 30, there are provided a plurality of removable ironpins 32 suitably spaced, preferably symmetrically positioned around themagnet, so as to short-circuit a desired portion of the flux produced bythe magnet. These pins 32, it will be noted, bridge the pole piece I1and the iron support 29 for the magnet.

Adjustment of the length of gap I3 is accomplished by rotation of theshaft 33. By rotating shaft 33 which connects to pinion 34, the ringgear 25 which is threaded to engage 34 will also rotate. Since ring gear25 is internally threaded, it engages the threads on iron disc 24, andit will be apparent that movement will be imparted to the iron disc 24.Th latter is kept from rotating by means of a pair of pins 36, only oneof which is shown in the drawing. Movement of the iron disc 24, however,will cause axial movement of th integrally connected iron sleeve 23 andbrass sleeve 3|. Since brass sleeve 3| is linked by threads to ironsleeve l9, it will be evident that axial movement of 23 and 3|, causedby movement of disc 24, will also cause axial movement of the copperplated iron sleeve I9 and thus produce a change in the width of the gapIS with a consequent change in the resonant frequency oi the cavityresonator 2. One of the pins 38 which prevents rotation of the iron disc24 has the additional function of rotating cylindrical ring gear 2| forvarying the length of the magnetic gap 20 between elements I9 and 2|.Ring gear 2| is internally threaded and rides on the threads of sleeves23 and 3|. An adjustment of the gap 23 changes the strength of themagnetic field in the plane of this gap. Since gap I6 is in series withgap 29. the magnetic field in the plane of gap It will also be changed.The magnitude of the 'magnetic field at both" gaps can be readjusted byincreasing or decreasing the number of shunts 32 across the magnet 30.Thus, by adjusting gap 29 and shunts 32 the proper magnetic field can beobtained at both gaps.

In order to cool the vacuum tube I, there is provided a metallicrectangular blower duct 3'! which has cooling air forced therethroughfrom a blower. This blower duct is mounted on one or more suitablemetallic studs 38 and communicates by means of aperture 39 and metalbellows 40 with the interior of the cavity resonator 2 through anotheraperture 4|. The blower thus produces a forced ventilation which causesair to flow through duct 31, through the bellows 42, through aperture 4|into the interior of resonator l2 and around the envelope of vacuum tubeat the location of the gap H5. The air then flows around the vacuum tubeenvelope 2 toward both the electron collector end and the grid end.Bellows 40 is made of a metallic material to prevent radiation of radiofrequency energy from the resonator l2. This bellows is rigidly fastenedto the resonator 2 at the cylinder I3 and acts as a flexible link toinsure a tight connection from the resonator to the duct 31. It shouldbe noted that theend of the bellows 40 which contacts the duct 31 isprovided with a sheet of metal 42 affixed thereto. Since the blower duct31 is rigidly fastened by means of stud. 38 to the cabinet or panel ofthe equipment it is a relatively simple matter to position the resonator|2 in its desired location and to flex the bellows 40 in such mannerthat the aperture in metallic sheet 42 registers with the aperture 39 inthe duct 31. In this way a single duct 31 provided with several spacedapertures 39 may serve to supply forced ventilation to a plurality ofspaced resonators |2 suitably located along the length of the ductopposite the spaced apertures 39.

In order to abstract energy from the cavity resonator |2 ther isprovided the output coupling coil or loop 45 which can be rotated bymeans of lever 46 to vary the coupling between the resonator and itsoutput coil support from maximum to a minimum. The output circuit iselectrically one-half wavelength long at the operating frequency asmeasured from the fixed ground point 41 around the loop 45 alongconductor 48 to the plunger disc 49. This output circuit may be a bandpass coupling circuit and is very generally the equivalent to that shownin copending application Serial No. 346,106, supra, except for certainrefinements which are described hereinafter. The coil 45 serves tocouple the tank circuit 2 to a suitable load or utilization circuitwhich may comprise an antenna connected to the output line 50. Thecoupling circuit includes a coaxial line comprising an inner conductor48 and an outer conductor 5|, the inner conductor of which iselectrically connected through a slider coupling link 52 to a metallicconductor 53 which, in turn, connects with one end of the loop 45. Theoutput line 50 is connected electrically to another point on the innerconductor 48 by means of a metallic spring clip 54. The plunger 49serves to short circuit the conductors and 5| in order to'change thedamping of the coupling circuit. In order to provide good electricalcontact between the plunger 49 and the inner surface of the conductor 5|of the coaxial line, there is employed a flexible metallic ribbon orstrip of sheet metal 55 which has transverse cuts therein so formed asto produce a multiplicity of resiliently bulging contact areas with thecircular areas engaging the conductor 5|. In this way there is obtainedboth good electrical contact at numerous points between the innersurface of the conductor 5| and the plunger 49 and also very smoothsliding or wiping action when it is desired to move the plunger. For amore detailed description of this type of sliding action, reference ismade to United States Patent No. 2,280,728. granted April 21, 1942, toA. Streib.

It should be noted that the free end of the inner conductor 48 of theoutput coupling circuit forms part of a concentric conductorcondenser,one'electrode of which includes a metallic plug 56electrically connected to the end of outer conductor 5|. By movingconductor 48 in or out of the plug 56, I am able to vary thecapacity'between the end of conductor 48 and the plug 56 and thus tunethe output circuit. In order to have movement of plunger 49 result inonly a change inthe damping of the circuit. means are provided to varysimultaneously both the plunger 49 and the'condenser 56, 48. Thus thetuning change which would result in a movement of plunger 49 is balancedby a change in condenser 56, 48. For this purpose there is provided aninternally threaded cylinder 51 which threadedly engages a hollowelement58 on its exterior surface, the latter in turn threadedly engaging theinner conductor 48 at 59. One end of the hollow element 58 is fixedlyattached to plunger 49 so that movement thereof will move the plungerand change the damping of the output coupling circuit. In order toprevent element 58 from rotating, there is provided a key Way 60 whichcooperates with a pin 6|. By rotating cylinder 51, axial movement of theplunger 49 will ensue, and simultaneously therewith, also axial movementof the conductor 48, with a consequent change in the capacity of theconcentric conductor condenser. However, since the capacity per unitlength of the condenser 56, 48 is greater than of the line 5|, 48, thiswould result in over correction for the tuning. Therefore, means areprovided to rotate 5! and 62 together while still leaving them free tomove axially with respect to each other. The pitch of thread 59 is finerthan the pitch of the thread of 51. Thus, when 51 and 62 are rotatedsimultaneously, the axial movement of 48 is less than the axial movementof 49. Thus, for a particular ratio of inside diameters of 56 and 5| theproper differential between the thread of 51 and the thread 59 can bechosen. If the inside diameter of 56 is equals to the inside diameter of5|, rotation of 5'! alone will result in the proper compensation oftuning when it is desired to change the damping. If it is desired merelyto change the tuning of the output coupling circuit without changing thedamping, this is done by rotating knurled knob 62 which varies thelength of the inner conductor 48 within plug 55. The circuit 52, 53, 45,41 will in general be a high impedance circuit.

It should be understood that the various features of the presentinvention can be utilized either alone or combined and that the vacuumtube I may be used in an ultra short wave system either as anoscillator, an amplifier, frequency converter, or a detector. Suchcircuits embodying the principles of the present invention have beenused with high eiiiciency at frequencies above 300 megacycles,particularly around 450 megacycles, though not limited thereto. Theelectrical connections necessary to complete the circuits for the vacuumtube have not been shown because they may follow any of the teachingsset forth in the copending applications supra, the invention not beinglimited thereto.

What is claimed is:

1. A hollow resonator having apertures in both sides thereof forming agap, an electron discharge device having an envelope extending acrosssaid gap, a cathode and a collector electrode in said envelope atopposite sides of said gap for causing an electron stream to traversesaid gap, spaced adjustable magnetic elements adjacent said sides ofsaid resonator and having a magnetic gap registering with the gap ofsaid resonator for providing a magnetic lens at said resonator gap andfor varying the width of the resonator gap, and movable means forvarying the distance between said spaced elements.

2. A hollow resonator having apertures in both sides thereof forming agap, means for causing an electron stream to traverse said gap, spacedadjustable magnetic elements adjacent said sides of said resonator andhaving a magnetic'gap registering with the gap of said resonator forproviding a magnetic lens at said resonator gap and for varying thewidth of the resonator gap, and movable means for varying the distancebetween said spaced elements for varying the width of said resonatorgapwithout moving any part of said resonator.

3. A hollow resonator having apertures in both sides thereof forming agap, means for causing an electron stream to traverse said gap,magneticmeans adjacent both sides of said resonator and having a gapregistering with the gapof said resonator for providing a magnetic lensat said gap, a resilient metallic element attached to one side of saidresonator and contacting said magnetic means at said same side, andmovable means for varying the width of the gap of said magnetic means.

4. A hollow resonator having a gap along the axis thereof, magneticmeans having a magnetic gap registering with the gap of said resonatorfor providing a magnetic lens thereat and also having a magnetic gapexternally of said resonator to provide another magnetic lens, means forcausing an electron stream to traverse the gaps of both lenses insuccession, and gears threadedly engaging said magnetic means forvarying the width of that magnetic gap registering with the gap of saidresonator for varying the tuning of said resonator without moving anypart of said resonator.

5. A hollow resonator having apertures in both sides thereof forming agap, means for causing an electron stream totraverse said gap, spacedadjustable magnetic elements adjacent said sides of said resonator andhaving a magnetic gap registering with the gap of said resonator forproviding a magnetic lens at said resonator gap and for varying thewidth of the resonator gap, and movable means for varying the distancebetween said spaced elements for varying the width-of said resonator gapwithout'moving any part of said resonator, said last means including athreaded element linked to one of said magnetic elements.

6. An electron discharge device having within an envelope a cathode forprojecting a beam of electrons and a collector electrode for receivingsaid beam, three spaced hollow members of mag netic material adjacentsaid envelope and surrounding the path of electrons and having positionslocated between said cathode and collector electrode, two adjacentmembers of said three being adjustable along the length of said beam,said spaced members providing a pair of magnetic gaps for focussing saidbeam, and gears threadedly engaging two of said members of magneticmaterial for varying the distances between any two of said threemembers.

7. A hollow. resonator having apertures in both sides thereof forming agap, means for causing an electron'stream to traverse said gap, spacedadjustable magnetic elements adjacent both sides of said resonator gapand having a gap registeringwith the gap of said resonatorw forproviding a magnetic lens at said resonator gap, a permanent magnetadjacent said magnetic elements,

and magnetic means shunting said magnet for varying the eil'ectiveamount of -magnetomotive force produced by said permanent magnet.

8. A hollow resonator having apertures in both sides "thereof forming 'agap, means for causing an electron stream to traverse said gap, spacedmagnetic elements adjacent both sides of said resonator gap and having agap registering with the gap of said resonator for proving a magneticlens at said resonator gap, a permanent magnet adjacent said magneticelements, and a plurality of removable magnetic pins bridging saidmagnet for sho'rt-circuiting a desired portion of .the flux produced bysaid magnet.

9.. A hollow resonator having apertures-in both sides thereof forming agap, means for causing an electron stream to traverse said gap, spacedmagnetic elements adjacent'both sides of said resonator gap and having agap registering with.

the gap of said resonator for providing a magnetic lens at saidresonator gap, adjustable means for varying the distance between saidmagnetic elements. without moving any part of said resonator, apermanent magnet adjacent said magnetic elements, and means in shunt tosaid magnet for varying the effective amount of magnetomotive forceproduced by said permanent magnet. 10. A hollow resonator havingapertures in both sides thereof forming a gap, an electron dischargedevice having an envelope extending across said gap, and means forcooling said device comprising a flexible hollow metallic link ,amxed atone end to and communicating with the interior of said resonator, ametallic sheet afiixed to the other end of said link, said sheet havingan aperture, an air duct having an aperture therein, and a blowerconnected to said air duct, the apertures of said metallic sheet andsaid duct registering with the aperture of said flexible link, wherebyair from said blower is forced into the interior of said resonator andflows around the envelope of said device at the location of said gap.

11. An electrondischarge device having within anenvelope a cathode forprojecting a beam of electrons and an electron collector, a hollow spaceresonator having a gap surrounding a portion of said envelope at alocation between said cathode andcollector, said resonator also having afluid inlet port remote from said gap and leading directly into saidresonator, and means connected to said port for forcing cooling fluiddirectly into said resonator through said port.

12. An electrondischarge device having a cavity resonator in circuittherewith, an energy transfer circuit coupled to said cavity resonator,said transfer circuit comprising a coaxial line having its innerconductor coupled to said resonator by means of a loop entering-theresonator. through an aperture, said inner conductor being inductivelycoupled to said resonator in said in terior by virtue of said loop,means forrotating said loop for varying the coupling between theresonator and said transfer circuit, said coaxial line having an openingin the outer conductor externally of said resonator, and a section ofanother coaxial line having its inner conductor coupled at onev end tothe-inner conductor of said transfer circuit through said opening andits outer conductor at'said same end coupled to the outer conductor ofsaid transfer circuit, and slidable, means within the coaxial line ofsaid transfer circuit for adjusting the effective length of the innerconductor of said transfer circuit as measured from said slidable meansto the junction point of the inner conductors of said coaxial lines. a

13. The combination with a hollow resonator of a coupling circuitcomprising a rotatable loop located in the interior of said resonatorand conductors forming acoaxial line connected to said loop, and tuningand damping means linked to the'conductors of said line. 1

14. An electron discharge ,device having a cavit'y resonator in circuittherewith, an energy transfer circuit coupled to said cavity resonator,

said transfer circuit comprising a coaxial line having its innerconductor coupled to said resonator by means of a loop entering theresonatorthrough an aperture, said inner conductor being inductivelycoupled to said resonator in said interior by virtue of said loop, meansfor rotatingsaid loop for varying the coupling between the resonator andsaid transfer circuit, said coaxial line having an opening in the outerconductor eX- ternally of said resonator, and a section of anothercoaxial line having its inner conductor coupled at one end to the innerconductor of said transfer circuit through said opening and its outerconductor at said same end coupled to the outer conductor of saidtransfer circuit, slidable means within the coaxial line of saidtransfer circuit for adjusting the effective length of a portion of saidtransfer circuit, and a tuning capacitor across one end of said transfercircuit, said capacitor being variable by movement of the innerconductor of the coaxial line of said transfer circuit.

15. Apparatus in accordance with claim 14, wherein means are providedmechanically linking the drive mechanism of said slidable means with thedrive mechanism of said variable condenser.

16. The-combination with a hollow resonator, of a band pass couplingcircuit including'ax'rotatable loop located in the interior of saidrosenator and acoaxial line connected to said loop, a short-circuitingbridge across said c'oaxialline, the length of said coupling circuit asmeasured from said bridge along said line and over: the length of saidloop to the remote'end of said loop being electrically one-halfwavelength at the mean operating frequency.

17. A hollow resonator having apertures-win both sides thereof forming agap, means for causing an electron stream to traverse said gap; spacedmagnetic elements adjacent both sides of said gap and having a gapregistering with the gap ofsaid resonator for providing a magnetic lensat said gap, a permanent magnet connected to said magnetic elements, anda removable magnetic pin bridging said magnet for short-circuit ing adesired portion of the flux produced by said magnet. w

18. A hollow resonator, means including a cathode on one side of saidresonator for projecting an electron stream through the interior of saidresonator, spaced magnetic elements surrounding a portion of the path oftravel of said stream and forming a gap, a permanentmagnet connected tosaid magnetic elements, and a removable magnetic pin bridging saidmagnet for short-circuiting a desired portion of the flux produced bysaid magnet. r

19; The combination with a hollow resonator of an energy couplingcircuit comprising arotatable loop located in theinterior ofsaidresonator and a stationary coaxial-line connected to said loop, andadjustable means connected to the conductors of said lineforvarying anelectrical characteristic of said line; I 1

20. The combination with a hollow resonator, of an energy couplingcircuit comprising a rotatable loop located in the interior of saidres'o nator and a coaxial line-connected to said loop, and tuning meansin circuit with said line for varying the capacity across theconductoi'soi said line. 3

' 1 r ORVILLE E;

